I had to look it up, here is what I found:<br />
Here were kept up the old games of hoodman blind, shoe the wild mare, hot cockles, steal the white loaf, bob apple, and snap dragon; the Yule-clog and Christmas candle were regularly burnt, and the mistletoe with its white berries hung up, to the imminent peril of all the pretty housemaids.<br />
So Washington Irving, in "Christmas Eve," relates the typical festivities surrounding the Twelve Days of Christmas, including kissing under the mistletoe (Washington Irving, The Sketch Book of Geoffrey Crayon, Gent). Irving continues his Christmas passage with a footnote:<br />
"The mistletoe is still hung up in farm-houses and kitchens at Christmas, and the young men have the privilege of kissing the girls under it, plucking each time a berry from the bush. When the berries are all plucked the privilege ceases."<br />
We moderns have conveniently forgotten the part about plucking the berries (which, incidentally, are poisonous), and then desisting from kissing under the mistletoe when the berries run out!
Horny guys I'm sure.
Um check wikipedia it lists everything!
it is odd, i'm going to google it later because I can't think of a single real use for mistletoe. As I understand it, it's quite toxic and so shouldn't be left around curious mouths.